From: Claudio Imbrenda <imbrenda@linux.ibm.com> To: Janosch Frank <frankja@linux.ibm.com> Cc: kvm@vger.kernel.org, cohuck@redhat.com, borntraeger@de.ibm.com, thuth@redhat.com, pasic@linux.ibm.com, david@redhat.com, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 05/13] KVM: s390: pv: handle secure storage exceptions for normal guests Date: Thu, 29 Jul 2021 15:28:35 +0200 [thread overview] Message-ID: <20210729152835.1f470ba8@p-imbrenda> (raw) In-Reply-To: <103c158c-dba6-7421-af8d-4d771c1cf087@linux.ibm.com> On Thu, 29 Jul 2021 14:17:11 +0200 Janosch Frank <frankja@linux.ibm.com> wrote: > On 7/28/21 4:26 PM, Claudio Imbrenda wrote: > > With upcoming patches, normal guests might touch secure pages. > > > > This patch extends the existing exception handler to convert the > > pages to non secure also when the exception is triggered by a > > normal guest. > > > > This can happen for example when a secure guest reboots; the first > > stage of a secure guest is non secure, and in general a secure guest > > can reboot into non-secure mode. > > > > If the secure memory of the previous boot has not been cleared up > > completely yet, a non-secure guest might touch secure memory, which > > will need to be handled properly. > > > > Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com> > > --- > > arch/s390/mm/fault.c | 12 +++++++++++- > > 1 file changed, 11 insertions(+), 1 deletion(-) > > > > diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c > > index eb68b4f36927..b89d625ea2ec 100644 > > --- a/arch/s390/mm/fault.c > > +++ b/arch/s390/mm/fault.c > > @@ -767,6 +767,7 @@ void do_secure_storage_access(struct pt_regs > > *regs) struct vm_area_struct *vma; > > struct mm_struct *mm; > > struct page *page; > > + struct gmap *gmap; > > int rc; > > > > /* > > @@ -796,6 +797,16 @@ void do_secure_storage_access(struct pt_regs > > *regs) } > > > > switch (get_fault_type(regs)) { > > + case GMAP_FAULT: > > + gmap = (struct gmap *)S390_lowcore.gmap; > > + /* > > + * Very unlikely, but if it happens, simply try > > again. > > + * The next attempt will trigger a different > > exception. > > + */ > > If we keep this the way it currently is then the comment needs to go > to the EFAULT check since it makes no sense above the > gmap_translate(). > > > + addr = __gmap_translate(gmap, addr); > > So we had a valid gmap PTE to end up here where the guest touched a > secure page and triggered the exception. But we suddenly can't > translate the gaddr to a vmaddr because the gmap tracking doesn't > have an entry for the address. > > My first instinct is to SIGSEGV the process since I can't come up > with a way out of this situation except for the process to map this > back in. The only reason I can think of that it was removed from the > mapping is malicious intent or a bug. > > I think this is needs a VM_FAULT_BADMAP and a do_fault_error() call. fair enough, the next version will have that > > + if (addr == -EFAULT) > > + break; > > + fallthrough; > > case USER_FAULT: > > mm = current->mm; > > mmap_read_lock(mm); > > @@ -824,7 +835,6 @@ void do_secure_storage_access(struct pt_regs > > *regs) if (rc) > > BUG(); > > break; > > - case GMAP_FAULT: > > default: > > do_fault_error(regs, VM_READ | VM_WRITE, > > VM_FAULT_BADMAP); WARN_ON_ONCE(1); > > >
next prev parent reply other threads:[~2021-07-29 13:29 UTC|newest] Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-07-28 14:26 [PATCH v2 00/13] KVM: s390: pv: implement lazy destroy Claudio Imbrenda 2021-07-28 14:26 ` [PATCH v2 01/13] KVM: s390: pv: avoid stall notifications for some UVCs Claudio Imbrenda 2021-07-29 9:58 ` Janosch Frank 2021-07-29 12:52 ` Claudio Imbrenda 2021-07-29 10:49 ` Cornelia Huck 2021-07-29 13:22 ` Claudio Imbrenda 2021-07-28 14:26 ` [PATCH v2 02/13] KVM: s390: pv: leak the ASCE page when destroy fails Claudio Imbrenda 2021-07-29 10:41 ` Janosch Frank 2021-07-29 12:54 ` Claudio Imbrenda 2021-07-29 13:45 ` Janosch Frank 2021-07-28 14:26 ` [PATCH v2 03/13] KVM: s390: pv: properly handle page flags for protected guests Claudio Imbrenda 2021-07-29 11:43 ` Janosch Frank 2021-07-28 14:26 ` [PATCH v2 04/13] KVM: s390: pv: handle secure storage violations " Claudio Imbrenda 2021-07-28 14:26 ` [PATCH v2 05/13] KVM: s390: pv: handle secure storage exceptions for normal guests Claudio Imbrenda 2021-07-29 12:17 ` Janosch Frank 2021-07-29 13:28 ` Claudio Imbrenda [this message] 2021-07-28 14:26 ` [PATCH v2 06/13] KVM: s390: pv: refactor s390_reset_acc Claudio Imbrenda 2021-07-28 14:26 ` [PATCH v2 07/13] KVM: s390: pv: usage counter instead of flag Claudio Imbrenda 2021-07-28 14:26 ` [PATCH v2 08/13] KVM: s390: pv: add export before import Claudio Imbrenda 2021-07-28 14:26 ` [PATCH v2 09/13] KVM: s390: pv: lazy destroy for reboot Claudio Imbrenda 2021-07-28 14:26 ` [PATCH v2 10/13] KVM: s390: pv: extend lazy destroy to handle shutdown Claudio Imbrenda 2021-07-28 14:26 ` [PATCH v2 11/13] KVM: s390: pv: module parameter to fence lazy destroy Claudio Imbrenda 2021-07-28 14:26 ` [PATCH v2 12/13] KVM: s390: pv: add OOM notifier for " Claudio Imbrenda 2021-07-28 14:26 ` [PATCH v2 13/13] KVM: s390: pv: add support for UV feature bits Claudio Imbrenda 2021-07-29 9:52 ` Janosch Frank 2021-07-29 13:28 ` Claudio Imbrenda
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